IE42740B1 - Process for producing aluminium chlorohydroxides - Google Patents

Abstract

1488444 Aluminium chlorohydroxide SNAMPROGETTI SpA 21 March 1975 [28 March 1974] 12043/75 Addition to 1410087 Heading ClA An aluminium chlorohydroxide of formula Al 2 (OH) x Cl y (in which x is 1-4 and y is 5-2) is prepared by reacting hydrochloric acid with an aluminium oxide or hydroxide at a temperature exceeding 160‹ C. but not exceeding 270‹ C., the amount of aluminium compound available for reaction with the hydrochloric acid being at least the stoichiometric amount needed to produce AlCl 3 . Preferably Bayer alumina is used.

Description

This invention relates to a process for the production of aluminium chlorohydroxides.

The specification of our Patent No. 37607, to which the present application is an application for a patent of- addition, describes and claims a process for producing an aluminium chlorohydroxide having the formula Al„(0II) Cl wherein x is in the range from 1 to 3.5 and y x y is in the range* from 5 to 2.5, which process comprises reacting hydrochloric acid with an aluminium compound selected from aluminium oxides and hydroxides, which optionally contains water of crystallization, wherein, relative to the hydrochloric acid, the aluminium compound is employed in an amount in' excess of that required stoichiometrically to produce aluminium trichloride, the amount of aluminium compound not exceeding 4 times that required stoichiometrically to produce aluminium trichloride.

In that process the amount of aluminium compound used is preferably at least twice, more preferably at least 2.5 times, the stoichiometric amount necessary for obtaining aluminium trichloride, and the reaction preferably takes place I at temperatures in the range from 100 to 160 °C. The aluminium starting compound can be, for example, Bayer alumina.

According to the present invention, there is provided a process for producing an aluminium chlorohydroxide having the formula A1„(OH)Cl in which x is in the range from 1 to 4 and x y y is in the range from 5 to 2, which process comprises reacting -2hydrochloric acid with an aluminium compound selected from aluminium oxides and hydroxides, and which optionally contains water of crystallization, the reaction being effected at a temperature exceeding 160°C but not exceeding 270°C, the aluminium compound available for reaction with the hydrochloric acid being employed in an amount, relative to the hydrochloric acid, corresponding to or in excess of the stoichiometric amount of aluminium compound required to produce aluminium trichloride.

The starting aluminium compound can he, for example, Bayer alumina; the use of Bayer alumina (α-AlgOg.31^0) allows the reaction to be carried out in a relatively short reaction time, and a good yield of basic aluminium chlorohydroxides to be obtained.

Preferably the hydrochloric acid is an aqueous solution of hydrochloric acid having a HC1 content of from 30 to 37% by weight.

The excess of the aluminium compound employed can be, for example, an excess of the aluminium compound of up to 50% over that required stoichiometrically to produce aluminium trichloride.

The reaction is carried out at a temperature exceeding 160°C and not exceeding 27O°C, preferably at a pressure in the range from 0.1 to 50 kg/cm .

At the end of the reaction, there remains a solid constituted fundamentally by unreacted alumina, which can be separated and fed again to a subsequent reaction.

The advantage of using Bayer alumina with respect to other aluminium compounds can bo seen from tho following: the use of, for example, bauxite in the reaction causes Lhe formation of a solid containing silica and alumina at a ratio depending on tho particular reaction conditions used and on the bauxite type. Tho different crystallographic structures and the different granulometry cause, as regards bauxite and the other aluminium compounds, a lower reaction rate which means, with tho reaction at the same temperature, longer reaction times, sometimes of the magnitude of 2 to 5 times as long as those required when using Bayer alumina.

The other working conditions and tho possible uses of the obtained chlorohydroxides are as described in our earlier application, to which reference is made for all further details.

The present invention will now be described by the following Examples.

EXAMPLE 1 Use was made of Bayer alumina with parLiclos having Ί0 te 70 μ diameter, The roaction was carried ml as follows: 00 kg of dry Bayer alumina (α-Α190.? . 311,,0) were reacted with 110 kg of an aqueous solution of hydrochloric acid, containing 33% by weight of hydrogen chloride. The reaction was carried out in an enamelled steel reactor having a useful capacity of 100 litres, equipped with an anchor stirrer rotating at 80 revolutions per minute, and by introducing into tho reactor nitrogen up to a pressure of 0.5 kg/cm . The temperature was -442740 raised from the room temperature to 180 °C over 30 minutes, and the reaction was continued l'or 4 hours at 180 °C, the final pressure being 8 kg/cm . At the end there was a precipitate constituted by unreacted Dayer alumina, corresponding to 1% of the fed alumina. The final product did not need any nitration and had an ΛΙ^Ο^ content equal to 10.5% ami a density, determined at 20°C, equal Lo 1.40 g/cc. Chemical analysis confirmed that, if was a chlornhydrnxi de having tile formula Al^ (OH)^Clg. More particularly, a full chemical analysis of tiie product resulting from the separation of the precipitate was as follows: ai203 10.5% (by weight) Cl 21..0% I'e 45 ppm Na 0.12% Ti 10 ppm Si 10 pH 0.9 EXAMPLE 2 rise was made of the same starting material as used in Example 1, and the following reaction was carried out: 800 g of dry Bayer alumina were reacted with 1000 g of hydrochloric acid in tlie form of an aqueous solution containing 37¾ by weight of hydrogen chloride. The reaction was carried out in a reactor made of Hastelloy B and equipped with a magnetic dragging stirrer rotating at a rate of 200 revolutions per minute. (The word Hastelloy is a Trade Mark), -5427 40 Before .starting the reaction, the air in the reactor was replaced by nitrogen up to a residual pressure of 0.5 kg/cm . ·The. temperature was then raised Crom room temperature to 230°C over 30 minutes, and the reaction was continued for 6 hours at 230 °C, the final pressure being 25 kg/cm2.

At the end the temperature was lowered to 80°C, and 700 g of distilled water were added. Chemical analysis showed a precipitate constituted by unreaeted Bayer alumina corresponding to 2% of the fed alumina. The final product did not need any filtration and had an Al^O^ content equal to 19.5% by weight, and a density at 20 °C equal to 1.41 g/cc. The chemical analysis confirmed an aluminium chlorohydroxide having the formula Al2(0iI)4Cl2· More particularly, the total chemical analysis of the product resulting from the separation of the precipitate was as follows: ai2o3 19.5% Cl 14.4% Fe 45 ppm Na 0.12% Ti 10 ppm Si 10 ppm pH 1.7 EXAMPLE 3 The starting material was bauxite, ground in particle having sizes of from 120 to 180 Mosh, having tin; Following composition (by weight) -642740 ΛΙ Og 65% Fe203 4% Si.O2 12% T102 2% Tho reaction was carried out by reacting 145 kg of bauxite with 100 kg of hydrochloric ;vcid containing in aqueous solution 37% by weight of hydrogen chloride. The operating conditions and reactor were the same as those described in Example 1.

After the introduction of N^fat 0.5 kg/cm^) into tlie reactor, the temperature was raised to 180°C over 30 minutes, and the reaction was continued for 45 hours at 100 °C.

Af the end of the reaction, it was noted that only 25% of the fed bauxite had been dissolved, and the residual was unroactod precipitate.

Chemical analysis of the suspension, after Lhe separation of tho precipitate, showed the following composition:AlgO 13.5% Cl 20.7% Ee 1.5% Chemical analysis of the precipitate gave tlie following composition: Al203 54% S i.Og 10% Fe 0.9% Ch lorohydroxide obtained by l.he reaction has the formula A 1.,(011), ..01, r.

Claims (8)

CLAIMS:

1. A process for producing an aluminium chlorohydroxide having the formula A1„(OH) Cl in which x is in the range fr « x y 1 to 4 and y is in the range from 5 to 2, which process 5 comprises reacting hydrochloric acid with an aluminium compo selected from aluminium oxides and hydroxides,and which optionally contains water of crystallization, the reaction being effected at a temperature exceeding 160°C but not exceeding 270°C, the aluminium compound available for reacti' 10 with the hydrochloric acid being employed in an amount, relative to the hydrochloric acid, corresponding to or in excess of the stoichiometric amount of aluminium compound required to produce aluminium trichloride.

2. A process according to claim 1, wherein the aluminium 15 compound available for reaction is employed in an amount up · 1.5 times that required stoichiometrically to produce alumin: trichloride.

3. A process according to claim 1, wherein the aluminium compound available for reaction is employed in an amount up 20 to twice that required stoichiometrically to produce aluminii trichloride.

4. A process according to claim 1, wherein the aluminium compound available for reaction is employed in an amount up i four times that required stoichiometrically to produce 25 aluminium trichloride.

5. A process according to any preceding claim, wherein tl reaction is carried out by using a hydrochloric acid solutioi 8 <1 2 7 4 0 having a concentration of from 30 to 37% by weight.

6. A process according to any preceding claim, wherein the aluminium compound is Bayer alumina.

7. A process according to claim 1, substantially as described in any one of the foregoing Examples.

8. An aluminium chlorohydroxide whenever produced by a process according to any preceding claim.